Dust mask



FIG. 1 is a perspective view of a dust mask showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The dash-dot lines represent a decorative stitch pattern on the surface of the mask in FIGS. 1-7. The even dashed line shown on the front of the mask in FIGS. 1, 2 and 4-6 form no part of the claimed design. 

CLAIM The ornamental design for a dust mask, as shown and described. 